I have moss growing already in cracks. Can’t powerwash because sand used to lay stone
Remove some of the sand and the moss. Then spray in a moss killer. Add polymeric sand to the gaps and wet down. It is sold at Lowe's and Home Depot. The moisture will react with sand and harden like cement. It helps hold the stones in place and provides a firm joint that can be power washed in the future.
Vinegar will fix that right up. Will kill the moss before you seal. Chances are you will still have moss growing but will be easier to treat if sealed.
So welcome Cathy! Good luck!